Strychnine acts by
**Core Concept**
Strychnine is a competitive antagonist of the inhibitory neurotransmitter glycine at the glycine receptors in the spinal cord, leading to an increase in excitatory neurotransmission and resulting in muscle convulsions and hyperreflexia.
**Why the Correct Answer is Right**
Strychnine competitively binds to the glycine receptor, a ligand-gated chloride channel, preventing the influx of chloride ions and thus reducing the inhibitory effect of glycine on spinal cord neurons. This results in an increase in excitatory neurotransmission, leading to muscle convulsions and hyperreflexia. The glycine receptor is a crucial component of the inhibitory neurotransmission system in the spinal cord, and strychnine's action on this receptor is responsible for its toxic effects.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** This option is not provided.
* **Option C:** This option is not provided.
* **Option D:** This option is not provided.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that strychnine's mechanism of action is distinct from that of other central nervous system depressants, such as barbiturates and benzodiazepines, which act on different receptors and have opposite effects on neurotransmission.
**Correct Answer:** A. Competitive antagonism of the glycine receptor.